Oxidizing-furnace.



No. 7120931 Patnfed Declan, |9021` J. F..4 GREENAWALT.

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(Application led Apr. 8. 1902.1

(No Model.) 4 Sllefssheet A TTOHNE Y Patented" Dec. 30, |902.

J. E. GHEENAWALT.

OXIDIZING FURNACE.

lApplcntion fled Apr. 8, 1902.:

4 Sheets-Sheet 2.

(No Model.)

A TTOHNE Y Patented Dec. 30, 1902. J. E. GREENAWALT.

DXIDIZING FURNACE.

Application filed Apr. 8, 1902.\

4 Sheets- Sheet 4.

(No. Model.)

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A TTORNE Y me cams Parme co. morouwo.. WASHINGTON. D. c.

Urrn *raras l ATnNT OFFICE.

JOHN E. GREENAWALT, OF DENVER, COLORADO, ASSIGNOR OF ONE-HALF TO VILLIAM ROBINSON, OF DENVER, COLORADO.

OXlDlZlNG-FURNACE.

SPECIFICATION forming part of Letters Patent No. 717,093, dated December 30, 1902.

Application iiled April 8, 1902. Serial No. 101,921. (No model.)

To all whom, it may con/cern:

Be it known that I, JOHN E. GREENAWALT, a citizen of the United States ofAmericanesiding at Denver, in the county of Arapahoe and State of Colorado, have invented certain new and useful Improvements in OXidizing-Furuaces; and I do declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in 1o the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to the figures of reference marked thereon, which form a part of this specification.

My invention relates to improvements in oxidizing-furnaces; and its object is the perfect and thorough oxidation of ores containing one or more valuable rnetals-such as gold, silver, or copper-as a necessary prezo liminary treatment to the successful extraction of these metals from refractory ores by means of chemical solutions. The roasting operation has an all-important bearing upon the subsequent recovery of the gold through z5 the medium of such solutions as chlorin and bromin. The consumption of these elements depends very largely upon the thoroughness andcompletenessoftheoxidizingprocess. Itis important that the sulfur be completely elimi- 3o nated and that the iron be converted into the soft porous ferrie oxid (Fe203) instead of the hard vitreous magnetic oXid,(Fe3O,) since the latter compound causes a large consumption of chlorin and large gold losses in the tailings. 3 5 M y researches on this point have proven that when a burning particle of iron sulfid is completely surrounded by a highly-oxidizing atmosphere at not too high a temperature the iron will be completely converted into ferrie 4o oxid, whereas if the burning particle is in a reducing, neutral, or even slightly-oxidizing atmosphere the magnetic oXid is rapidly formed.

In my improved oxidizing-furnace the particles of ore fall through a strong oxidizing atmosphere at a sufficiently high temperature to start and maintain combustion until the combustible elements have been completely oxidized.

The furnace consists of five distinct partsfirst, the hot air compartments, Where an abundance of superheated air and steam is producedfor the roasting-compartments; second, the roasting-compartxnents, where the ole particles are passed through the highly-oxidizing atmosphere; ythird, the dustchamber, where the solid particles of ore are allowed to settle preparatory to returning them to the roasting compartments; fourth, the acidtower, where all the metallic fumes and intensel y fine solid particles of ore are condensed and a dilute solution of sulfurous and sulfuric acid produced, and, fifth, the hotore pit.

Having thus briefly outlined the nature of the invention, the objects sought, and the main features of the mechanical construction, I will proceed to describe the same in detail, reference being made to the accompanyingI drawings, in which is illustrated an embodiment thereof.

In the drawings, Figure 1 is a vertical longitudinal section of the furnace, taken on the line .fr Fig. 2. Fig. 2 is a horizontal section taken on the line y y, Fig. 1. Fig. 3 is avertical cross-section taken on the line z z, Fig. 2, viewed in the direction of the arrow. Fig. 4 is a vertical section taken on the line R R, Fig. 2, viewed in the direction of the arrow. Fig. 5 is a similar section taken on the line C D, Fig. 2. Fig. 6 is a section taken on the line A B, Fig. 2, viewed in the direction of the arrow. Fig. 7 is a section taken on the line D D, Fig. l.

The same reference characters indicate the same parts in all the views.

Let the numeral 5 designate the hotair compartmentsLwhich are two in number and of the same construction in every respect. Each of these compartments consists of a combustion-chamber or firebox 5 and a large space 5C, lled with brick checker-work, in which the bricks are so arranged as to occupy about half the space. To the upper end of the stack portion of each of these chambers or compartments is fastened a truncated casting 5J', provided with an orifice sufciently large to carry away the gases from the fire when the checker-work is heating. Above this casting is a suitable lid or ,covering 6, which will be termed a valve. One of these valves is constructed to accurately fit IOO into and close the opening in the top o f each stack. Above the valves are wheels or pulleys 7, over which passes a leXible cable 8, to the ends of which are respectively fastened the two valves 6, so that by moving the cable the opening of one stack is opened, while the other is closed. The upper ends of these stacks are connected by means of suitable conduits 9 to a fan or blower 10. The lower portions of the hot-air compartments 5 are respectively connected with the adjacent roasting-compartments by means of iues 13. These two iues are controlled by a damper 14, which is adapted to open one and close the other. By moving this damper back and forth in a recess l5 one of the ues is closed and the other opened.

The ore-roasting part of the furnace preferably consists of three vertical shaft-com partments 16, 17, and 18. .The bottom of the compartment 16, which I for convenience term the first compartment, is connected with the top of the second compartment 17 by means ot' an iron chain or bucket elevator 19, which takes the hot and partially-roasted ore from the bottom of the compartment 16 and elevates it to the top of the compartment 17; also, the bottom of the compartment 17 is connected with the top of the compartment 18 by means of an elevator 20. The discharge-spout of the elevator 19 is connected with a suitable pipe 22 to carry the ore from the elevator tothe compartment 17 by means of a screw conveyer 17, which spreads the ore and scatters it over the entire chamber, thus exposing each particle independently to the heated gases. In like manner the ore is discharged from the elevator 2O to the roasting-compartment 18 by a pipe 22a and a con- Veyer 17. The completely-roasted ore finally falls upon the bottom of the compartment 18, where it mingles with the 'fine dust from a I dust-chamber and together pass into the hot ing temperature and in case of highly-sili-v `a spout 51 into an ore-bin or other suitable receptacle. (Not shown.) The top of the compartment 17 communicates with the top of a dust-flue 23, which conducts the furnacegases into a dust-chamber 24. The lower part of the compartment 17 is connected with a supplemental combustion-chamber or firebox 25 by means of a iiue 26. The object of this supplemental combustion-chamber is to bring the compartment 17 to the proper workcious ores to assist in maintaining the temperature in this compartment.

The dust-receptacle 24 is a large chamber where the velocity of the furnace-gases is reduced sufciently to allow the Vsolid particles to separate from the gases. This dust-chamber consists of two wings 24b and 24C. In the first wing 24b the heavier particles fall to the chute 24 and thence pass into one compartment 27a of the con veyer-trough 27. The conveyer 27g consists of two chains with Hight attachments moving through the trough, the iights pushing the material through' the trough. The ore particles in the compartment 27a of the conveyertrough are conveyed to an opening 27d. (Indicated by dotted lines in Fig. 1, but not otherwise shown.) These ore particles are discharged from the compartment 27a of the conveyer into the boot of the elevator 2O of the compartment 17. This elevator delivers the ore to the roasting-compartment 18 through the instrumentality of the discharge-pipe 22, whereby the fine ore particles are continuously worked through the furnace.

The intensely ne dust which collects in the second wing 24c of the dust-chamber falls upon the chute 24e and thence into a compartment 27c of the conveyer trough 27, whence it is conveyed to the screw 43, by means of which it is delivered to the bottom of the compartment 18, where it mingles with the body of the ore coming through the furnace and passes with it into the hot-ore pit 45. The fine dust contains a large proportion of sulfates, which are very desirable for the decomposition of the sodium chlorid, which is added to the ore as it drops into the pit, thus releasing the necessary chlorin to chloridize the silver and other elements while the ore is in the pit.

Near-the roof ofthe dust-chamber is a sheetmetal pipe 28, whose object is to reduce the temperature of the furnace-gases before passing them into the acid-tower and also to transfer some of the waste heat in the furnacegases to the current of -pure air inside the pipe, which air may be used for heating the buildings and supplying Various combustionchambers with heated air. The air is'circulated through this pipe by a suitable fan. (Not shown.) The draft in the furnace is secured bya large exhaust-blower 30, which draws the furnace-gases and forces them through the condensing or acid tower 31.

` The interior of this tower is filled with checker brickwork 31d. The brickwork is kept wet by a stream of water sprinkled upon the top of the brickwork from a pipe 31g, the tower being open at the top for the purpose. wet brick condense the metallic fumes from the gases as the latter pass through and among them.

The solution will absorb some of the sulfuric and sulfurous acid from the gases, also hydrochloric acid, if the ore is given a chloridizing roasting. The furnace-gases finally pass into the atmosphere at the top of the acid-v tower.

The operation of the furnace is as follows:

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The ore is first crushed, so that it will pass through a twenty or thirty mesh screen, and then elevated to the top of the furnace by an elevator 21 and dropped into the middle compartmentl. Hereitmeetsthefurnace-gases and falls downward with the gases to the bottom of the shaft, Where it is deflected by an inclined wall16a and discharged into the path of the elevator 19, which raises it to the top of the furnace and drops it in to the next compartment17. Thetemperatureinthecompartment 16 is kept just high enough-say from 400 to 600 Fahrenheitto start the combustion of the ore particles. In fact, the theory of this furnace is to surround each individual particle with a highly-oxidizing atmosphere maintained at the necessary temperature to continue the burning of the ore particle in its passage through the furnace Yuntil the oxidization iscompleted. Thefurnace-gases passfromthe first compartment 16 by way of a iiue lcinto the compartment 17, near the bottom of the furnace. The ore in falling through this compartment 17 meets the rising furnace-gases. It is necessary to maintain a higher temperature in this compartment-say from 500o to 800 Fahrenheit. Hence the function of the supplemental combustion-chamber 25. However, when the sulfur contents of the ore are high this fireplace 25 is not required, as the oxidizing of the sulfur and base metals produces ample heat. From the bottom of the compartment 17 the ore is taken by the elevator 20 and delivered to the top of the third compartment 18. In this compartment the ore is also exposed to a finishing heat, or from 1,200 to 1,4:00O Fahrenheit, and to a superabundance of oxygen, which is introduced fresh from the hot-air compartments. IVith certain ores it is desirable to introduce asmall amount of producer-gas to maintain the temperature in the lower part of this compartment. rlhis may be done by way of a pipe 34. (Shown in Fig. 1.)

The operation of the hot-air compartments is as follows: The fire in one of them being started, the flue 13, leading from one to the roasting-compartment, is closed by the damper 14, while the valve 6 at the top of the checker-work is opened. The fuel-gases from the ire then pass through and among the checker-work, bringing the brickwork up to a high temperature. When this brick checkerwork has been brought to the required temperature, the fire-box doors are closed, the flue 13 opened, the valve 6 at the top closed, and the corresponding blast-gate 12 opened, so that the blast of cold air and steam from the blower 10 is forced up the pipe 19 and down through the checkeuwork, getting hotter and hotter in its passage through the brickwork, until it finally leaves the red hot bricks through the flue 13 among the red-hot particles of falling ore in the roastingcompartment. WVhile the air is passing through one of the hot-air compartments, the fire is being applied to the other, so that by alternating every two hours a continuons stream of superheated air is introduced into the roastingcompartments.

To one side of the wall of the roasting-com partments 16, 17, and 18 is formed a brick housing 35, inclosing the vertical elevators 19, 20, and 21. The bottom of the space inclosed by this housing communicates with the roasting compartments 16, 17, and 18 by means of openings 36, through which the ore passes from the inclined bottoms 16, 17, and 18' of the roasting-chambers. The brick housing 35 projects above the top of the roasting chambers or compartments to facilitate the discharge from the elevators into the top of one compartment or the other, as may be desired. In like manner a housing 37 is formed between the two wings of the dust-chamber to receive the contents of the latter, which pass through openings 38 at the lower extremities of the inclined bottoms 24a and 24.0. This housing 37 incloses the conveyer 27 and extends forward or to the left (see Figs. 1 and 2) of the dust-chamber in order to discharge into the boot of the elevator 20 and into the screw conveyer 4.3, as heretofore described.

Having thus described my invention, what I claim is- 1. In a stack oxidizing-furnace, the combination of two or more shaft-compartments, a dust-chamber compartment, means to elevate the hot and partially-roasted ore falling at the bottom of one of the shaft-compartments, to the top of another shaft-compartment, and means to collect the hot and partially-roasted dust falling in the dust-compartment and elevate it to the top of one of the shaft-compartments.

2. In a stack oxidizing-furnace, the combination of two or more shaft-compartments, a dust-chamber compartment, a vertical elevator extending from the bottom of one compartment to the top of the next compartment, and ahorizontal conveyer to collect the dust in the dust-compartment and convey it to the vertical elevator.

3. In a stack oxidizing-furnace, the combination of two or more shaft-compartments, a dust-chamber compartment, 4an elevator located outside the wall of said compartments, and extending upwardly to the top thereof, and an opening at the bottom of one compartment to allow the ore to pass therefrom to the elevator for the purpose set forth.

4t. In a stack oxidizing-furnace, the combination of two or more shaft-compartments, a dust-chamber compartment, an elevator to convey the ore from the bottom of one compartment to the top of another compartment, and means to distribute and scatter the ore at the top of the compartment to which it is elevated.

5. In a stack oxidizing-furnace, the combination of two or more shaft-compartments, a dust-chamber compartment, means to elevate the hot and partially-roasted ore falling at the bottom of one of the shaft-compartments,

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to the top of another shaft-compartment, and means to collect the hot and partially-roasted dust falling in the dust-compartment and elevate it to the top of one of the shaft-cornpartments, and means to distribute and seatter the ore at the topy of the shaft-compartments.

6. In a stack oxidizing-furnace, the combination of two or more vertical ore-roasting compartments,an elevator connecting the bottom of one to the top of another, an air-heatingc0mpartment,aCombustion-chamber communicating with the air heating compartment, a ue connecting the air-heating compartment With the ore-roasting compartment, a damper to open and close said flue, and a valve at the' end of the heating-compartment opposite the combustion-chamber.

'7. In an oXidizing-furnaoe,the combination of a roasting-compartment, a dust-chamber consisting of two sections, means for returning the dust from one section to the roastingeompartment, and means to deliver the dust from the other section to the hot roasted ore coming from the roasting-compartment.

8. In an oXidizing-furnace,the combination of a roasting-compartment, a dust-chamber 

